Control circuits and methods for voltage converters

ABSTRACT

Control circuits and methods for voltage converters. In some embodiments, a control system or circuit can be implemented for a voltage converter, and can include a driving unit configured to generate a driving signal having a pulse width and a frequency. The driving signal can be provided to a voltage conversion circuit to control conversion of an input voltage into an output voltage. The control system or circuit can further include a modulation unit configured to modulate the pulse width of the driving signal based on the output voltage to thereby allow adjustment of the output voltage. The control system or circuit can further include a frequency control unit configured to adjust the frequency of the driving signal based on the modulated pulse width.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.14/287,253 filed May 27, 2014, entitled VOLTAGE CONVERTER, the benefitof the filing date of which is hereby claimed and the disclosure ofwhich is hereby expressly incorporated by reference herein in itsentirety.

TECHNICAL FIELD

This application relate to the field of electronic technique, and moreparticularly to a voltage converter and a control method used therein.

BACKGROUND

Electronic devices typically include modules such as differentsubsystems, circuits and so on. For example, tablet computers, smartphones, music players etc. may include therein power amplifiers,monitors and so on. Respective modules of an electronic apparatustypically require different supply voltages for achieving normaloperations thereof. For example, an analog power amplifier may require asupply voltage of 3.5 volt, a digital processing module may requiredifferent supply voltages of 1.8 volts, 5 volts etc. Moreover, when anelectronic apparatus is in different operation modes, the supplyvoltages required by the respective modules may also vary.

An electronic apparatus is often equipped with a power supply with aspecific voltage, for example, in a battery-powered electronicapparatus, the battery may probably only supply a voltage of 3.9 voltsto 4.5 volts. To ensure the normal operations of the respective modulesin the electronic apparatus, a voltage converter is required to converta direct current (DC) voltage level (e.g., a voltage from the battery)into another different DC voltage as required by an individual module,that is, a specific input voltage Vin is converted into a differentoutput voltage Vout.

In the conventional voltage converters, for example, electric energy atan input port is transitorily stored in an inductor and/or a capacitor(i.e., a charging process is performed), and thereafter electric energyis released at a different voltage at an output port (i.e., adischarging process is performed), so that the input voltage Vin isconverted into the desired output voltage Vout. Accordingly, drivingsignals are employed to drive a control component (e.g., a switch), bywhich the charging process and the discharging process are controlled soas to obtain the desired output voltage Vout, that is, a turn-on timeTon during which a corresponding switch is turned on to charge and aturn-off time Toff during which the switch is turned-off to dischargeare controlled. The turn-on time Ton corresponds to a pulse width of thedriving signals.

In some voltage converters, a situation where the input voltage Vin isvery close to the output voltage Vout may occur. In this situation, theturn-on time Ton needs to be shortened so as to ensure the stable outputvoltage Vout, especially when a load driven by the output voltage Voutis relatively light. However, as limited for example by the reactiontime or the like characteristics of an electronic element, a minimumTon_min of the turn-on time Ton can only be a finite value. In thiscase, the voltage converters charge and then discharge with the minimumturn-on time at a part of a work cycle, and halt the charging anddischarging at the other part of the work cycle, in order to provide abalanced average power, which causes the output voltage to be unstableand causes big ripples to appear. A single charging process and a singledischarging process are implemented in each work cycle, and as the workcycle of the voltage converter gets shorter and shorter, that is, theswitching frequency becomes higher and higher, the aforesaid problembecomes particularly prominent.

SUMMARY

Aspects of the present application may relate to a voltage converter,application of the voltage converter in each module of an electronicapparatus, and a control method adopted in the voltage converter.

In a voltage converter of the present application, a pulse width (i.e.,the turn-on time Ton) can be detected in each work cycle T, T=Ton+Toff,a switching frequency fsw can be adjusted based on the detected pulsewidth Ton, the switching frequency fsw is used for controlling the workcycle of the voltage converter and equal to a reciprocal of a work cycleT, i.e., fsw=1/(Ton+Toff), thereby the switching frequency is reducedwhen the input voltage Vin is very close to the output voltage Vout orthe load driven by the output voltage Vout is relatively light, thusachieving a relatively low duty ratio, and thereby ensuring a stableoutput voltage.

In the present application, the duty ratio can be reduced by adjustingthe switching frequency based on the pulse width, such that the dutyratio is not limited by the minimum pulse width Ton_min, thus it ispossible to maintain a stable frequency switching, and accordinglyreduce a switching loss.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly explain the application, drawings used todescribe the embodiments or the conventional technologies are brieflyintroduced below. The drawings described below are merely someembodiments of the present disclosure, and a person of ordinary skill inthe art can also obtain other drawings according to these drawings.Identical reference numerals typically indicate identical componentsthroughout the various drawings.

FIG. 1 is a schematic diagram illustrating an example where a voltageconverter is used for driving a lighting device in an electronicapparatus;

FIG. 2 is a schematic diagram illustrating an example where a voltageconverter is used for driving an amplifier in an electronic apparatus;

FIG. 3 schematically illustrates a block diagram of a voltage converterin the present application;

FIG. 4 schematically illustrates an example of a voltage conversioncircuit in the voltage converter shown in FIG. 3;

FIG. 5 schematically illustrates a block diagram of a frequency controlunit in the voltage converter shown in FIG. 3;

FIG. 6 schematically illustrates a pulse width threshold value adoptedin the frequency control unit shown in FIG. 5;

FIG. 7 illustrates a schematic circuit diagram of the frequency controlunit in the voltage converter in the present application;

FIG. 8 illustrates a first simulation result of performing voltageconversion by the voltage converter in the present application;

FIG. 9 illustrates a second simulation result of performing voltageconversion by the voltage converter in the present application; and

FIG. 10 illustrates a flowchart of an example operation method of thevoltage converter in the present application.

DETAILED DESCRIPTION Applications of the Voltage Converter in anElectronic Device

Circuits, methods, apparatus and so on applicable to the voltageconverter as described herein can be implemented in various electronicapparatuses, such as mobile telephones, tablet PCs, monitors, e-readers,portable digital media players, etc. Hereinafter, application of thevoltage converter in an electronic apparatus will be described brieflywith reference to FIGS. 1 and 2.

FIG. 1 is a schematic diagram illustrating an example where a voltageconverter is used for driving a lighting device in an electronicapparatus. The lighting device is for example an light emitting diode(LED), which is for example used in an electronic apparatus such as asmart phone, a camera etc. In FIG. 1, a power supply 10 provides theinput voltage Vin, a voltage converter 20 receives the input voltageVin, and converts it into the output voltage Vout to drive the LED 30.The power supply 10 is, for example, a battery, and it may also be anyother power supply capable of providing DC.

FIG. 2 is a schematic diagram illustrating an example where a voltageconverter is used for driving an amplifier in an electronic apparatus.In FIG. 2, the power supply 10 provides the input voltage Vin to thevoltage converter 20, which converts the input voltage Vin into theoutput voltage Vout to drive an amplifier 40.

The power supply 10 may be a battery in the electronic apparatus or anyother power supply capable of providing DC. The amplifier 40 may be apower amplifier used in a smart telephone for amplifying a radiofrequency (RF) signal having a relatively low power (RF_in in FIG. 2)into a RF signal having a higher power. The amplified RF signal (RF_outin FIG. 2) can be used for various purposes, e.g., driving antenna of atransmitter in a smart telephone. Accordingly, in a smart phone having3G, 4G communications standards, the power amplifier can be used foramplifying the RF signal. Since a desired transmission power level mayvary depending on a distance that the user is away from a base station,it is desirable to variably control a gain of the power amplifier foramplifying the RF signal.

In practice, the voltage converter shown in FIG. 1 or 2 can bemanufactured in a chip, and can also be integrated on a module togetherwith an object driven by it (e.g., LED 30 or amplifier 40), its specificimplementation does not constitute a limitation to the presentapplication.

In the description illustrated above with reference to FIGS. 1 and 2,the load driven by the voltage converter is illustrated with the LED andthe amplifier as example. However, the voltage converter can drive anyother modules or devices that can be configured to operate with a DCvoltage.

Voltage Converter

FIG. 3 schematically illustrates a block diagram of a voltage converterin the present application. As shown in FIG. 3, the voltage converter 20may include: a voltage conversion circuit 21 for converting the inputvoltage Vin into the output voltage Vout to drive the load, with theconverting operation being controlled by using a driving signal; amodulation unit 22 for modulating a pulse width of the driving signalbased on the output voltage Vout, and outputting a pulse widthindication signal indicative of the modulated pulse width; a frequencycontrol unit 23 for generating a frequency control signal FQ_Controlwhich is used to adjust the switching frequency of the driving signalbased on the pulse width indicated by the pulse width indication signal;a frequency generator 24 for generating the switching frequency based onthe frequency control signal FQ_Control; and a driving unit 25 forgenerating the driving signal based on the pulse width indication signalfrom the modulation unit 22 and the switching frequency from thefrequency generator 24. The respective units or parts in the voltageconverter 20 will be further described below.

FIG. 4 schematically illustrates an example of the voltage conversioncircuit 21 in the voltage converter 20 shown in FIG. 3. As shown in FIG.4, the voltage conversion circuit 21 may include: an inductor L forreceiving the input voltage Vin, being connected to ground via a triodeT1, and being charged during the turn-on time Ton and discharged duringthe turn-off time Toff; a capacitor C, one end of which being connectedto a connection point of the inductor L and the triode T1 (i.e., a pointSW in FIG. 4) via a triode T2, and the other end of which beinggrounded, and for ensuring a stable output of the output voltage Vout.The triodes T1 and T2 are control devices for controlling the voltageconversion circuit 21, and control the voltage conversion operation ofthe voltage conversion circuit 21 under the driving of the above drivingsignals. The converting operation may include the following chargingprocess and discharging process.

During the charging process, a first driving signal in the drivingsignal causes the triode T1 to turn on, that is, a conducting path isformed between the inductor L and the ground to produce an inductivecurrent; a second driving signal in the driving signal causes the triodeT2 to turn off, that is, an open path is formed between the connectionpoint (i.e., the point SW in FIG. 4) of the inductor L and the triode T1and a port of the outputs voltage Vout, and the capacitor C is preventedfrom discharging with respect to the ground. Since the input voltage Vinis a direct current, the inductive current on the inductor L linearlyincreases in a certain rate which is related to an inductance value ofthe inductor L, and energy is stored in the inductor L as the increaseof the inductive current.

During the discharging process, the first driving signal in the drivingsignal causes the triode T1 to turn off, that is, an open path is formedbetween the inductor L and the ground; the second driving signal in thedriving signal causes the triode T2 to turn on, that is, a conductingpath is formed between the connection point (i.e., the point SW in FIG.4) of the inductor L and the triode T1 and the port of the outputvoltage; because of a holding characteristic of the induction current,the current flowing through the inductor L will not immediately becomezero, but will instead slowly decrease from a value when the charging iscompleted, until a next charging process starts or the current valuedrops to zero; since the triode T1 is turned off, the inductor L candischarge only through the capacitor C, correspondingly, the inductor Lstarts charging the capacitor C, thereby boosting a voltage between twoends of the capacitor C.

The inductor L absorbs energy during the above charging process, andreleases energy during the above discharging process. If the chargingprocess and the discharging process are repeated continually, the outputvoltage Vout higher than the input voltage Vin can be obtained acrossthe capacitor C. That is to say, a boost conversion is achieved.

The voltage conversion circuit 21 described above with reference to FIG.4 is only a schematic illustration, for example, the triodes T1 or T2therein may be replaced with a switch or a diode. If the triodes T2 isreplaced with a diode, the second driving signal can be omitted. Thevoltage conversion circuit 21 in FIG. 3 may also be implemented as abuck conversion circuit 21 where the output voltage Vout is lower thanthe input voltage Vin, or may be implemented as a boost-buck conversioncircuit 21 when necessary, which involves changing the positionalrelationship between the capacitor C and the inductor L accordingly.Furthermore, the voltage conversion circuit 21 in FIG. 3 may alsoinclude more inductors, capacitors, triodes etc., especially in aboost-buck converter. Accordingly, the driving signal may include moredriving signals besides the first and second driving signal.

The modulation unit 22 compares the output voltage Vout with a desiredsupplied voltage Vref, modulates the pulse width of the driving signalsaccording to the comparison result, and outputs a pulse width indicationsignal indicative of the modulated pulse width.

The modulation unit 22 may for example include an error comparator,which compares the output voltage Vout with a preset reference voltage(corresponding to the desired supplied voltage) and obtains a comparisonresult. Furthermore, a voltage divider circuit may also be adopted forsupplying a part of the output voltage Vout to the error comparator tomake a comparison, and the preset reference voltage may also varyaccordingly.

When the output voltage Vout deviates from the desired supplied voltageVref, the modulation unit 22 modulates the pulse width of the drivingsignals based on deviation information. In the voltage conversioncircuit 21 described with reference to FIG. 4, the pulse widthindication signal indicative of the modulated pulse width can beobtained based on the comparison result from the error comparator andthe current at a grounded terminal of the triode T1. Specifically, aresistor is disposed between the triode T1 and the ground to obtain asensed signal of the inductive current, and compares this sensed signalwith the comparison result from the error comparator so as to generatethe pulse width indication signal. Alternatively, in the voltageconversion circuit 21 described with reference to FIG. 4, the pulsewidth indication signal indicative of the modulated pulse width may alsobe obtained by comparing the comparison result from the error comparatorwith a preset reference signal (e.g., a sawtooth wave signal).

The modulation unit 22 may typically include a pulse width modulator(PWM), with which the pulse width of the driving signals can bemodulated based on the comparison result. As an example, when the outputvoltage Vout is greater than the desired supplied voltage Vref, thepulse width modulator can reduce the pulse width of the driving signals;when the output voltage Vout is lower than the desired supplied voltageVref, the pulse width modulator can increase the pulse width of thedriving signals. Other modulators instead of the pulse width modulatormay also be used for modulating the pulse width, and specific types ofthe modulator do not constitute a limitation to the present application.

FIG. 5 schematically illustrates a block diagram of the frequencycontrol unit 23 in the voltage converter 20 shown in FIG. 3. As shown inFIG. 5, the frequency control unit 23 may include: a detector 231 fordetecting whether the pulse width indicated by the pulse widthindication signal outputted from the modulation unit 22 is within apredetermined range; and a control signal generator 232 for generating afrequency control signal FQ_Control for adjusting the switchingfrequency of the driving signals when the pulse width outputted from thepulse width modulation unit 22 exceeds the predetermined range.

As described above, when the input voltage Vin is very close to theoutput voltage Vout, or the load driven by the output voltage Vout isrelatively light, during the work cycle including a charging process anda discharging process, the voltage converter circuit 21 in the voltageconverter 20 needs to have a small duty ratio D to maintain the stableoutput voltage Vout, where D=Ton/(Ton+Toff), Ton is the turn-on timeduring which the control device (e.g., triode T1 in FIG. 4) is turned onto charge, Toff is a turn-off time during which the control device isturned off to discharge. As limited by characteristics of an electronicelement such as the reaction time thereof, a minimum Ton_min of theturn-on time Ton is typically a finite value. When the turn-on time Tonis less than the minimum value Ton_min, the voltage converter 20typically does not work normally.

When the pulse width indicated by the pulse width indication signaloutputted from the modulation unit 22 is close to the minimum Ton_min,the input voltage Vin is very close to the output voltage Vout or theload driven by the output voltage Vout is relatively light, then theduty ratio D needs to be reduced. Thus, a first threshold value P_th1can be set for the pulse width, and the first threshold value P_th1 canbe greater than but close to the minimum value Ton_min. Thepredetermined range may be that the pulse width is greater than or equalto the first threshold value P_th1 accordingly, so that when thedetector 231 detects that the pulse width indicated by the pulse widthindication signal outputted from the pulse width modulation unit 22 isnot within the predetermined range (this pulse width is smaller than thefirst threshold value P_th1), the control signal generator 232 generatesa frequency control signal FQ_Control for adjusting the switchingfrequency of the driving signals. As an example, when the minimumTon_min is 10 nanoseconds (ns), the first threshold value P_th1 may beset to 20 ns, 25 ns, etc., and a proper threshold value P_th1 may bedetermined based on the minimum turn-on time Ton_min according torequirements.

Since D=Ton·fsw, where fsw is a switching frequency at which a controldevice (e.g., triode T1 in FIG. 4) in the voltage conversion circuit 21operates, when the detector 231 detects that the pulse width indicatedby the pulse width indication signal outputted from the modulation unit22 is less than the first threshold value P_th1, the duty ratio can belowered by reducing the switching frequency fsw, so as to maintain thestable output voltage Vout. That is to say, when the detector 231detects that the pulse width indicated by the pulse width indicationsignal outputted from the modulation unit 22 is less than the firstthreshold value P_th1, the control signal generator 232 generates afrequency control signal FQ_Control for reducing the switching frequencyof the driving signals.

The operations and specific implementations of the frequency controlunit 23 will be further described below.

The frequency generator 24 generates a switching frequency based on thefrequency control signal FQ_Control. The frequency control signalFQ_Control corresponds to a specific operation mode of the frequencygenerator 24, so as to ensure that the frequency control signalgenerator 24 can accurately operate based on the frequency controlsignal FQ_Control. The frequency generator 24 may be implemented withthe existing techniques or a variety of techniques that may appear inthe future, and its specific implementations do not constitute alimitation to the present application.

The driving unit 25 may generate the driving signals according to thepulse width indicated by the pulse width indication signal from thepulse width modulation unit 22 and the switching frequency from thefrequency generator 24. The driving signals generated by the drivingunit 25 correspond to the control devices in the voltage conversioncircuit 21. For example, in the case where the transistors T1, T2 in thevoltage conversion circuit 21 are to be controlled as described abovewith reference to FIG. 4, the driving signals generated by the drivingunit 25 include the first driving signal and the second driving signal.Specifically, the pulse width of the first driving signal generated bythe driving unit 25 is the pulse width indicated by the pulse widthindication signal, and the switching frequency of the first drivingsignal is the switching frequency from the frequency generator 24;thereafter, the second driving signal can be obtained by inverting aphase of the first driving signal. In a case where there are morecontrol devices in the voltage conversion circuit 21, the drivingsignals generated by the driving unit 25 will include more drivingsignals, in addition to the first driving signal and the second drivingsignal. Implementations of the driving unit 25 do not constitute alimitation to the application.

In addition, other modules may be included in the voltage converter 20if necessary. For example, when the voltage converter 20 needs to switchbetween different operating modes, it may also include a mode switchingmodule and a mode control module for controlling the mode switching.

According to the above description, it can be known that the frequencycontrol unit 23 can learn the situation that the input voltage Vin isclose to the output voltage Vout or the situation of a light load bydetecting the pulse width, and can decrease the duty ratio by reducingthe switching frequency so as to maintain the stable output voltageVout. In this case, even if the pulse width of the driving signals isclose to the minimum turn-on time Ton_min, it is also possible tomaintain the stable output voltage by further reducing the switchingfrequency fsw, so that the operation of the voltage converter 20 is notlimited by the minimum turn-on time Ton_min. In this process, in thecase that the input voltage Vin is close to the output voltage Vout orin the case of a light load, the switching frequency fsw can begradually reduced, rather than being directly suspended during certainwork cycle in the conventional voltage converters, its frequencyconversion can be very stable, and has low switching loss, which will bedescribed later in details.

In the above descriptions with reference to FIGS. 3-5, for the sake ofclarity, the modulation unit 22 and the driving unit 25 (surrounded bydashed lines in FIG. 3) are illustrated as being included in the voltageconverter 20. However, the modulation unit 22 and the driving unit 25may be external to the voltage converter 20, and connected to thevoltage conversion circuit 21 and the frequency control unit 23 etc.through signal lines.

Frequency Control Unit in the Voltage Converter

Operations and illustrations associated with the frequency control unit23 will be further described below.

In the implementation of the current digital circuit, when the detector231 in FIG. 5 detects that the pulse width indicated by the pulse widthindication signal outputted from the modulation unit 22 is less than thefirst threshold value P_th1, the control signal generator 232 willgenerate a frequency control signal FQ_Control for halving the switchingfrequency, so as to halve the switching frequency through the frequencygenerator; and after a predetermined time period (e.g., 400 μs, 600 μs,etc.), the detector 231 detect again whether the pulse width indicatedby the pulse width indication signal outputted from the modulation unit22 is less than the first threshold value P_th1. If the pulse width isstill less than the first threshold value P_th1, the control signalgenerator 232 continues to generate a frequency control signalFQ_Control for halving the switching frequency; and the process isrepeated until the detector 23 detects that the pulse width indicated bythe pulse width indication signal outputted from the modulation unit 22is more than or equal to the first threshold value P_th1. Furthermore,if the frequency generator 24 has a minimum switching frequency fsw_min,this minimum switching frequency will also be considered in the aboverepetition process. Correspondingly, the detection operation of thedetector 231 and the adjustment operation of the control signalgenerator 232 are repeated, until the pulse width indicated by the pulsewidth indication signal outputted from the modulation unit 22 is morethan the first threshold value P_th1, or the switching frequency isreduced to the minimum switching frequency fsw_min.

In addition to reducing the switching frequency by way of halving theswitching frequency, the frequency generator 24 can also reduce theswitching frequency by way of reducing it by a specific value, andcorrespondingly, the frequency control signal FQ_Control generated bythe control signal generator 232 instructs the frequency generator 24 toreduce the switching frequency by a specific value.

In the above operation process of the frequency control unit 23, after astable output voltage is maintained by reducing the switching frequencyfsw, if the pulse width modulated by the modulation unit 23 is caused toincrease due to an increase of the load driven by the output voltageVout or other reasons, for example, the detector 231 detects that thepulse width indicated by the pulse width indication signal is more thana second threshold value P_th2, which is greater than the firstthreshold value P_th1, the control signal generator 232 may control thesignal generator 232 to generate a frequency control signal FQ_Controlfor doubling the switching frequency; and after a predetermined timeperiod (e.g. 400 μs, 600 μs, etc.), the detector 231 detect againwhether the pulse width indicated by the pulse width indication signalis greater than the second threshold value P_th2. If the pulse width isstill greater than the second threshold value P_th2, the control signalgenerator 232 generate again a frequency control signal FQ_Control forfurther doubling the switching frequency, and the detection and thegeneration of frequency control signal FQ_Control doubling are repeateduntil the detector 231 detects that the pulse width indicated by thepulse width indication signal is less than or equal to the secondthreshold value P_th2. In addition, if the frequency generator 24 has amaximum switching frequency fsw_max, it will be also considered in theabove repetition process, and correspondingly, the detection operationof the detector 231 and the generation operation of the control signalgenerator 232 will be repeated, until the detector 231 detects that thepulse width indicated by the pulse width indication signal is less thanor equal to the second threshold value P_th2, or the switching frequencyis increased to the maximum switching frequency.

As described above, the second threshold value P_th2 of the pulse widthis greater than the first threshold value P_th1 thereof. For example,the second threshold value P_th2 may be set to be more than a double ofthe first threshold value P_th1, so as to meet the hysteresisrequirement in the voltage conversion circuit 21. For example, thesecond threshold value P_th2 may be equal to 3*P_th1, 4*P_th1 and so on.As can be seen, when the detector 231 detects whether the pulse widthindicated by the pulse width indication signal is within a predeterminedrange, the detector 231 may detect whether the pulse width indicated bythe pulse width indication signal is less than the first threshold valueP_th1 only, or may detect both whether the pulse width indicated by thepulse width indication signal is less than the first threshold valueP_th1 and whether it is greater than the second threshold value P_th2.

A reason for the process of generating the frequency control signalFQ_Control to increase the switching frequency fsw as described abovelies in: the voltage converter 20 typically has a default switchingfrequency fsw default, the various components of the voltage converter20 can have good performance at this default switching frequency, thevoltage converter 20 therefore preferably operates at the defaultswitching frequency or at a frequency close to the default switchingfrequency; when the duty ratio needs to be increased, the switchingfrequency of the voltage converter 20 is preferred to be increased andthe pulse width thereof is reduced correspondingly, thereby the voltageconverter 20 will have excellent performance.

FIG. 6 schematically illustrates two pulse width thresholds in thefrequency control unit 23 of the voltage converter 20 as shown in FIG.5. As shown in FIG. 6, the pulse width of a pulse signal PULSE1 has afirst threshold value P_th1, the pulse width of a pulse signal PULSE2has a second threshold value P_th2, which is more than a double of thefirst threshold value P_th1. The detector 231 in the frequency controlunit 23 may compare the pulse width indicated by the pulse widthindication signal with the first threshold value P_th1, or compare thesame with both the first threshold value P_th1 and the second P_th2, soas to determine whether the pulse width indicated by the pulse widthindication signal is within a predetermined range.

FIG. 7 illustrates a schematic circuit diagram of the frequency controlunit 23 in the voltage converter 20 in the present application.

As shown in FIG. 7, in the detector 231, whether the pulse widthindicated by the pulse width indication signal PWS outputted from themodulation unit 22 is less than the first threshold value P_th1 of pulsesignal PULSE1 is detected by using a logic “AND” gate AND1 whichperforms a logic “AND” operation on the pulse width indication signalPWS outputted from the modulation unit 22 and the pulse signal PULSE1;after inverting the pulse signal PULSE2 by using an inverter INV,whether the pulse width indicated by the pulse width indication signalPWS outputted from the modulation unit 22 is greater than the secondthreshold value P_th2 of pulse signal PULSE2 is detected by using alogic “AND” gate AND2 which performs a logic “AND” operation on thepulse width indication signal PWS outputted from the modulation unit 22and the inverted signal of the pulse signal PULSE2.

In the control signal generator 232, two logic “AND” gates AND3 and AND4are used for transferring the determination result to a D flip-flop, andthereby generating a frequency increasing signal for increasing theswitching frequency and a frequency decreasing signal for decreasing theswitching frequency, a counter outputs a final frequency control signalFQ_Control according to the frequency increasing signal or the frequencydecreasing signal, a sample delayer serves for spacing a predeterminedtime interval (e.g. 400p, 600p, etc.) between two adjacent operations ofchanging the frequency, thereby avoiding a control confusion caused byfrequently increasing/decreasing the switching frequency.

In the frequency control unit 23 in FIG. 7, when the detector 231detects that the pulse width indicated by the pulse width indicationsignal PWS outputted from the modulation unit 22 is less than the firstthreshold value P_th1 of pulse signal PULSE1, the control signalgenerator 232 controls by using the D flip-flop, and outputs a frequencydecreasing signal and, makes the counter to halve the switchingfrequency or reduce the switching frequency by a specific value, so asto output the frequency control signal FQ_Control. Meanwhile, a resetsignal resets a sample delay block, and thereafter delays for apredetermined time period for a next sampling; when the detector 231detects that the pulse width indicated by the pulse width indicationsignal PWS outputted from the modulation unit 22 is more than the secondthreshold value P_th2 of pulse signal PULSE2, the control signalgenerator 232 controls by using the D flip-flop, and outputs a frequencyincreasing signal, and makes the counter to double the switchingfrequency or increase the switching frequency by a specific value, so asto output the frequency control signal FQ_Control. Correspondingly, areset signal resets the sample delay block, and thereafter delays for apredetermined time period for a next sampling. And so on, and so forth.

FIG. 8 illustrates a first simulation result of performing voltageconversion by the voltage converter having the frequency control unit 23shown in FIG. 7. In FIG. 8, the horizontal axis represents time; thelongitudinal axis in FIG. 8(a) represents voltage. FIG. 8(a) showscurves of the input voltage Vin and the output voltage Vout. Thelongitudinal axis represents current in FIG. 8(b), which shows a curveof the load current. The longitudinal axis represents voltage in FIG.8(c), which shows the curve of the voltage at the point SW shown in FIG.4, and the curve reflects the switching frequency of the voltageconverter 20. As can be seen, after the input voltage Vin is close tothe output voltage Vout, the stable output voltage Vout is ensured byreducing the switching frequency fsw, the output voltage Vout in thevoltage converter 20 has small ripples, and the frequency switching ofthe voltage converter 20 is very stable and has low switching lossaccordingly.

FIG. 9 illustrates a second simulation result of performing voltageconversion by the voltage converter having the frequency control unit 23shown in FIG. 7. In FIG. 9, the horizontal axis represents time; and thelongitudinal axis represents the voltage in FIG. 9(a), which shows thecurves of the input voltage Vin and the output voltage Vout; thelongitudinal axis represents the current in FIG. 9(b), which shows acurve of load current; the longitudinal axis represents the voltage inFIG. 9(c), which shows the curve of the voltage at a point SW shown inFIG. 4, where the curve reflects the switching frequency of the voltageconverter 20. As can be seen, after the input voltage Vin is close tothe output voltage Vout and the switching frequency is at its minimumvalue, if the input voltage Vin decreases and is deviated from itsoutput voltage Vout, then the switching frequency fsw is increasedgradually and it is operated at a switching frequency close to or equalto its default switching frequency. This ensures a stable output voltageVout with small ripples, and the switching frequency is very stable andthe voltage converter has low switching loss accordingly.

Control Method Employed in the Voltage Converter

FIG. 10 illustrates a flowchart of an example operation method 100 ofthe voltage converter 20 in the present application. As shown in FIG.10, the operation method 100 of the voltage converter 20 may include:converting the input voltage Vin into the output voltage Vout to drivethe load, with the converting operation being controlled by drivingsignal (1001); modulating the pulse width of the driving signal based onthe output voltage Vout, and outputting a pulse width indication signalindicative of the modulated pulse width (1002); generating a frequencycontrol signal FQ_Control for adjusting the switching frequency of thedriving signal based on the pulse width indicated by the pulse widthindication signal (1003); generating the switching frequency based onthe frequency control signal FQ_Control (1004); and generating thedriving signal for controlling the converting operation based on thepulse width indication signal and the switching frequency (1005).

In 1003, generating the frequency control signal FQ_Control foradjusting the switching frequency of the driving signals based on thepulse width indicated by the pulse width indication signal may include:detecting whether the pulse width is within a predetermined range; whenthe pulse width exceeds the predetermined range, generating thefrequency control signal FQ_Control for adjusting the switchingfrequency of the driving signal.

The detecting whether the pulse width indicated by the pulse widthindication signal is within a predetermined range may include: detectingwhether the pulse width indicated by the pulse width indication signalis less than a first threshold value P_th1, which is determined by aminimum turn-on time Ton_min of a switch in the voltage converter 20.Alternatively, whether the pulse width indicated by the pulse widthindication signal is within a predetermined range may include detectingboth whether the pulse width indicated by the pulse width indicationsignal is less than a first threshold value P_th1 and whether the pulsewidth indicated by the pulse width indication signal is more than thesecond threshold value P_th2, with the second threshold value P_th2being greater than the first threshold value P_th1, and preferably ismore than a double of the first threshold value P_th1.

When the pulse width indicated by the pulse width indication signal isless than the first threshold value P_th1, the generating the frequencycontrol signal FQ_Control for adjusting the switching frequency of thedriving signals may include: generating a frequency control signalFQ_Control for halving the current frequency or reducing it by otheramounts. When the pulse width indicated by the pulse width indicationsignal is greater than the second threshold value P_th2, the generatingthe frequency control signal FQ_Control for adjusting the switchingfrequency of the driving signals may include: generating a controlsignal FQ_Control for doubling the current switching frequency orincreasing it by other amounts. Moreover, the detection is repeatedafter a predetermined time period, and when the pulse width indicated bythe pulse width indication signal exceeds the predetermined range, thefrequency control signal FQ_Control for adjusting the switchingfrequency of the driving signals is generated again, until the modulatedpulse width is within the predetermined range.

When the voltage converter works by in accordance with the method 100,the case that the input voltage Vin is close to the output voltage Voutand the case of a light load can be learned by detecting the pulsewidth, and the duty ratio can be lowered by reducing the switchingfrequency so as to maintain the stable output voltage Vout, so that theoperation of the voltage converter is not limited by the minimum turn-ontime Ton_min. Since the switching frequency fsw can be graduallyreduced, rather than being directly suspended during a certain workcycle in the conventional voltage converters, its frequency conversionis very stable, and the voltage converter has low switching loss.

In the various examples described herein, references are made totriodes. It will be understood that such triodes can include transistorssuch as field-effect transistors (FETs). Such FETs can include, forexample, MOSFET devices and/or transistors implemented in other processtechnologies. Other types of transistors can be utilized to implementone or more features of the present disclosure.

A person skilled in the art can understand that, for the convenience andsimplicity of description, the specific implementations of embodimentsof the method described above can be referred to the correspondingprocess in foregoing product embodiments.

Some or all of the steps of the method described with reference to FIG.10 can used in the voltage converter described with reference to FIGS.3-7, and can be used in any other voltage converter. Said method may beexecuted and completed by a hardware modules or a combination ofhardware modules and software modules. The software modules may residein a random access memory, a flash memory, a read only memory, aprogrammable read-only memory or an electrical erasable programmablememory, a register among other sophisticated storage medium in the art.

As can be appreciated by a person of ordinary skill in the art, devicesand algorithm steps described in combination with the exemplaryembodiments disclosed herein can be implemented by way of electronichardware, or a combination of computer software and electronic hardware.These functions are to be executed by hardware manner or software mannerdepends upon the particular application and design constraints of thepresent application. A person skilled in the art can use different waysto achieve the described functions with respect to each specificapplication, but such implementation should not be construed as goingbeyond the scope of the present invention.

Principles and advantages of the application described hereinabove areapplicable to any system and apparatus that needs DC-DC voltageconversion. Such systems with DC-DC voltage converters can beimplemented in various electronic apparatuses. The electronicapparatuses can include, but are not limited to, consumer electronicproducts, parts of the consumer electronic products, electronic testequipment. The consumer electronic products can include, but are notlimited to, a smart phone, a television, a tablet computer, a monitor, apersonal digital assistant, a camera, an audio player, a memory and thelike. The consumer electronic products can include a multi-chip module,a power amplifier module, and an integrated circuit including a voltageconverter.

The above described are only specific implementations of the presentapplication, but the scope of the present application is not limitedthereto, and any alternatives and equivalents that can be easilyconceivable by a person skilled in the art within the technical scopedisclosed by the present application should be encompassed within thescope of protection of the present application.

1. A control system for a voltage converter, comprising: a driving unitconfigured to generate a driving signal that includes a plurality ofpulses, each pulse having a width, the driving signal being provided toa voltage conversion circuit to control conversion of an input voltageinto an output voltage; a modulation unit configured to modulate thewidth of at least some of the pulses of the driving signal with a pulsewidth indication signal that is based on the output voltage to therebyallow adjustment of the output voltage; and a frequency control unitconfigured to generate a frequency control signal based on the pulsewith indication signal, the frequency control signal configured toadjust a frequency of the driving signal.
 2. The control system of claim1 further comprising a frequency generator configured receive thefrequency control signal and decrease or increase the frequency of thedriving signal.
 3. The control system of claim 1 wherein the frequencycontrol unit includes a detector configured to receive the pulse widthindication signal and compare it to first and second threshold pulseshaving widths representative of lower and upper limits of a selectedrange, respectively.
 4. The control system of claim 3 wherein frequencycontrol signal is configured to provide a decrease in the frequency ofthe driving signal when the pulse width indication signal indicates thatthe modulated pulse width is less than the first threshold pulse width.5. The control system of claim 4 wherein the decrease in the frequencyof the driving signal allows a duty ratio of the voltage conversioncircuit to be decreased without further decrease in the modulated pulsewidth below the first threshold pulse width.
 6. The control system ofclaim 5 wherein the first threshold pulse width is selected to begreater than a minimum turn-on time of the voltage conversion circuit.7. The control system of claim 5 wherein the first threshold pulse widthis selected relative to a minimum turn-on time of the voltage conversioncircuit to allow regulation of the output voltage when the outputvoltage is close to the input voltage or when a load driven by theoutput voltage is relatively low.
 8. The control system of claim 3wherein the frequency control signal is configured to provide anincrease in the frequency of the driving signal when the pulse widthindication signal indicates that the modulated pulse width is greaterthan the second threshold pulse width.
 9. The control system of claim 8wherein the increase in the frequency of the driving signal allows aduty ratio of the voltage conversion circuit to be increased beyond anincrease provided by an increase in the modulated pulse width alone. 10.The control system of claim 1 wherein the detector includes a first ANDgate and a second AND gate, the first AND gate generating a first outputthat is an AND-combination of the pulse width indication signal and thefirst threshold pulse, the second AND gate generating a second outputthat is an AND-combination of the pulse width indication signal and aninverse of the second threshold pulse.
 11. The control system of claim10 wherein the frequency control unit further includes a control signalgenerator having a logic circuit configured to receive the first andsecond outputs of the detector and generate the frequency controlsignal.
 12. A voltage converter comprising: a voltage conversion circuitconfigured to convert an input voltage into an output voltage; and acontrol system configured to control the voltage conversion circuit, thecontrol system including a driving unit configured to generate a drivingsignal that includes a plurality of pulses, each pulse having a width,the driving signal being provided to control the conversion of the inputvoltage into the output voltage, the control system further including amodulation unit configured to modulate the width of at least some of thepulses of the driving signal with a pulse width indication signal thatis based on the output voltage to thereby allow adjustment of the outputvoltage, the control system further including a frequency control unitconfigured to generate a frequency control signal based on the pulsewith indication signal, the frequency control signal configured toadjust a frequency of the driving signal.
 13. The voltage converter ofclaim 12 wherein the input voltage is a DC voltage.
 14. The voltageconverter of claim 15 wherein voltage conversion circuit is configuredsuch that the output voltage is less than or greater than the inputvoltage.
 15. An electronic device comprising: a load configured toutilize a regulated voltage; and a voltage converter configured toreceive a supply voltage and generate the regulated voltage for theload, the voltage converter including a voltage conversion circuitconfigured to receive the supply voltage as an input voltage andgenerate the regulated voltage as an output voltage, the voltageconverter further including a control system configured to control thevoltage conversion circuit, the control system including a driving unitconfigured to generate a driving signal that includes a plurality ofpulses, each pulse having a width, the driving signal being provided tocontrol the conversion of the input voltage into the output voltage, thecontrol system further including a modulation unit configured tomodulate the width of at least some of the pulses of the driving signalwith a pulse width indication signal that is based on the output voltageto thereby allow adjustment of the output voltage, the control systemfurther including a frequency control unit configured to generate afrequency control signal based on the pulse with indication signal, thefrequency control signal configured to adjust a frequency of the drivingsignal.
 16. The electronic device of claim 15 further comprising a powersupply circuit configured to provide a battery voltage as the supplyvoltage.
 17. The electronic device of claim 15 wherein the load includesa lighting device powered by the regulated voltage.
 18. The electronicdevice of claim 17 wherein the lighting device includes a light emittingdiode.
 19. The electronic device of claim 15 wherein the load includes aradio-frequency component powered by the regulated voltage.
 20. Theelectronic device of claim 19 wherein the radio-frequency componentincludes a radio-frequency amplifier.